FeIIS-II + 12 HNVO3 FeIII(NVO3)3 + H2SVIO4 + 9 NIVO2 + 5 H2O

This is an oxidation-reduction (redox) reaction:

S-II - 8 e- SVI (oxidation)

9 NV + 9 e- 9 NIV (reduction)

FeII - 1 e- FeIII (oxidation)

Change the oxidation states